1. Field of the Invention
The present invention relates to an ink jet printer head, and more particularly to an ink jet printer head for discharging an ink droplet of an improved shape by a fluid pressure of air or the like, resulting in a high resolution print.
2. Description of the Related Art
Generally, an ink jet printer head is divided into a thermal type or a piezo-actuator type. A thermal ink jet printer head discharges ink in such a manner that a thin-film heater resistor instantly heats the ink, generating and expanding ink bubbles. A piezo-actuator ink jet printer head discharges ink by displacement of a piezo-actuator.
A thermal ink jet printer head exemplary of contemporary practice in the art discharges ink through a nozzle hole in such a manner that a thin-film heater resistor instantly heats ink of an ink chamber, generating and expanding ink bubbles. Accordingly, as the expanded ink bubbles pressure the ink chamber, the ink is discharged through the nozzle hole.
Also, a piezo-actuator ink jet printer head exemplary of contemporary practice in the art discharges ink through a nozzle hole in such a manner that electric power is applied to a piezo-actuator which is disposed on a silicon plate and opposite to a nozzle plate, thereby displacing the piezo-actuator. Accordingly, an ink chamber is pressured and the ink is discharged through a nozzle hole.
Since the thermal and piezo-actuator ink jet printer heads exemplary of contemporary practice in the art simply push the ink to discharge, a tail of an ink droplet is generated when the ink bubbles vanish or the displacement of the piezo-actuator is stopped. Since the tail of the ink droplet is usually lengthened and fragmented by a surface tension and a viscosity, a high resolution print typically can not be obtained.
U.S. Pat. No. 4,339,762 to Shirato et al. entitled Liquid Jet Recording Method disclose a liquid jet recording method capable of recording gradation includes filling with a liquid a conduit having, at the end, an orifice for ejecting and projecting a liquid droplet to a predetermined direction, the conduit being provided with a heat actuating portion generating a force for ejecting the liquid droplet by applying heat energy to the liquid to cause an abrupt state change. The heat actuating portion includes an electrothermal transducer having a heat generating portion such that the degree of heat supply is different from position to position on the heating surface, and controlling the strength of an input electric signal corresponding to the gradation of an image to be recorded.
U.S. Pat. No. 4,847,630 to Bhaskar et al. entitled Integrated Thermal Ink Jet Printhead And Method Of Manufacture disclose an integrated thermal ink jet printhead and manufacturing process which includes the successive build-up of an orifice plate, a first barrier layer, heater resistors, a second barrier layer, and an ink reservoir-defining layer on top of a reusable or xe2x80x9cdummyxe2x80x9d substrate. Lead-in conductors are formed integral with the heater resistors and openings are formed between ink reservoirs and the orifice plate to provide for ink flow under control of the heater resistors.
U.S. Pat. No. 4,882,595 to Trueba et al. entitled Hydraulically Tuned Channel Architecture disclose the use of lumped resistive elements in an ink feed channel between an ink-propelling element, such as a resistor, and an ink supply plenum. A secondary constriction in the ink feed channel is defined by a width sufficient to provide physical support for the resistive elements while avoiding resistance to ink refill. The printhead includes lead-in lobes for assisting in purging any bubbles in the ink.
U.S. Pat. No. 5,479,196 to Inada entitled Ink Jet Recording Apparatus And Method Of Recovery Ink Discharging Condition Of The Same discloses an ink jet recording apparatus that has a recording head provided with a plurality of ink discharging openings, ink paths leading to the ink discharging openings and an ink chamber commonly connected to the ink paths. Each ink path has a recording thermal energy generating element for causing film boiling of ink in the ink path so as to form a bubble of the ink vapor thereby discharging an ink droplet from the discharging opening. Tiny bubbles generated in each ink path as a result of the driving form a comparatively large void with which at least a part of the ink in each ink path is replaced so that stagnant bubbles are merged in the void and, hence, extinguished. The recording head can have an assisting thermal energy generating element which cooperates with the recording thermal energy generating element.
U.S. Pat. No. 5,760,804 to Heinzl et al. entitled Ink-Jet Printing Head For A Liquid-Jet Printing Device Operating On The Heat Converter Principle And Process For Making It disclose an ink print head of a sandwich type construction according to the bubble-jet principle. The heating elements and the shoot out openings are arranged so as to be laterally offset relative to one another in such a way that the spreading direction of the steam bubble is directed opposite to the ink shooting direction.
U.S. Pat. No. 5,850,241 to Silverbrook entitled Monolithic Print Head Structure And A Manufacturing Process Therefor Using Anisotropic Wet Etching discloses printing heads which operate using coincident forces, whereby nozzles are etched through a silicon substrate, allowing two dimensional arrays of nozzles for color printing, and drive transistors, shift registers, and fault tolerance circuitry can be fabricated on the same wafer as the nozzles.
U.S. Pat. No. 5,912,685 to Raman entitled Reduced Crosstalk Inkjet Printer Printhead discloses an ink jet printer printhead which employs two ink feed channels to couple an ink firing chamber to the source of ink. A first one of the ink feed channels has a lower fluid resistance to ink flowing in the channel than a second one of the ink feed channels. The first ink feed channel and the second ink feed channel each have an inlet to the ink source and are arranged such that the inlet of the first ink channel is closer to the ink firing chamber than the inlet of the second ink feed channel. Adjacent ink firing chambers are arranged such that a lower fluid resistance ink channel of one ink firing chamber is next to a higher fluid resistance ink channel of a neighboring ink firing chamber.
U.S. Pat. No. 5,956,058 to Momose et al. entitled Ink Jet Print Head With Improved Spacer Made From Silicon Single-Crystal Substrate disclose an ink jet printer head that includes a spacer including pressure generating chambers continuous to nozzle openings, ink supply paths, and reservoirs, a cover member for covering the pressure generating chambers in a sealing fashion, and pressure generating means for generating pressure in the pressure generating chambers in accordance with print data. One of the walls of a path hole for forming a pressure generating chamber is aligned with one of the walls of a path hole for forming a reservoir. Walls defining the path hole for forming a pressure generating chamber, which are located in the vicinity of a nozzle opening, are connected to each other at an obtuse angle.
U.S. Pat. No. 6,019,457 to Silverbrook entitled Ink Jet Print Device And Print Head Or Print Apparatus Using The Same discloses an ink jet print device that includes a passageway for flowing ink having an outlet for ejecting ink at one end. The passageway has a portion where the cross-sectional dimensions of the passageway change. A generating device which generates energy for ejecting ink from the outlet is disposed on a surface intersecting the passageway and defines a part of the portion where the cross-sectional dimensions of the passageway change.
European Patent Application EP 0 652 108 A2 to Momose et al. entitled Ink Jet Print Head And A Method Of Manufacturing The Same disclose an ink jet printer head that includes a spacer including pressure generating chambers continuous to nozzle openings, ink supply paths and reservoirs, a cover member for covering the pressure generating chamber in a sealing fashion, and pressure generating means for generating pressure in the pressure generating chambers in accordance with print data. One of the walls of a path hole for forming a pressure generating chamber is aligned with one of the walls of a path hole for forming the ink supply path. Walls defining the path hole for forming a pressure generating chamber, which are located in the vicinity of a nozzle opening, are connected to each other at an obtuse angle.
The present invention promotes overcoming the above-described problem in the above described ink jet printer heads of the related art. Therefore, it is an object, among other objects, of the present invention to provide an ink jet printer head for discharging of ink droplets of a uniform shape by a fluid pressure of air pressure or liquid pressure, for example, resulting in a high resolution print.
It is another object, among other objects, of the present invention to provide a method for discharging of ink droplets of a uniform shape from an ink jet printer head, by a fluid pressure of air pressure or liquid pressure, for example.
To accomplish the above object, and other objects of the present invention, the present invention provides an ink jet printer head including a nozzle plate having a plurality of nozzle holes or nozzle openings, a base plate disposed adjacent to the plurality of nozzle holes for defining an ink flow path and an ink chamber, and an ink discharge device disposed correspondingly to the nozzle plate across the base plate, for discharging ink of the ink chamber through the nozzle hole or the plurality of nozzle holes by a fluid pressure by contacting the ink with a fluid.
According to the present invention, the ink discharge device includes a through-hole or aperture or a plurality of through-holes or apertures formed in the base plate correspondingly to a nozzle hole or to a plurality of nozzle holes, a fluid chamber defined in or on a side of the base plate to be charged with the fluid, an opening valve or a plurality of opening valves for selectively opening and closing a corresponding through-hole or a corresponding plurality of through-holes, and an operation unit for operating a corresponding opening valve.
According to a preferred embodiment of the present invention, the operation unit includes an actuator for selectively ascending and descending the opening valve. It is preferable that the actuator includes a piezo-actuator layered on the opening valve, a plurality of electrode plates for driving the piezo-actuator, and a power supply for applying electric power to the electrode plates.
Another object, among other objects, of the present invention also provides a method for discharging ink from an ink jet printer head including the steps of: selectively supplying and charging ink to an ink chamber which is formed between or in communication with a base plate and a nozzle plate having a nozzle hole or opening or having a plurality of nozzle holes or nozzle openings; pressuring the ink of the ink chamber by partially contacting the ink with a fluid; discharging the ink of the ink chamber through the nozzle hole or the plurality of nozzle holes; and releasing pressure of the fluid in the ink chamber.